iotaCSS is now a monorepo and all individual repositories are part of it. Please open issues or PRs here: https://github.com/iotacss/iotacss.
The display utility contains helper classes for the CSS display property.
npm install --save iotacss-utils-display
$iota-utils-display-namespace : '' !default;
$iota-utils-display-block-name : 'block' !default;
$iota-utils-display-hidden-name : 'hidden' !default;
$iota-utils-display-inline-name : 'inline' !default;
$iota-utils-display-inline-block-name : 'inline-block' !default;
$iota-utils-display-res : false !default;
$iota-utils-display-breakpoints : $iota-global-breakpoints !default;
.u-block
.u-hidden
.u-inline
.u-inline-block
// Responsive Class Syntax
.u-[name]@[breakpoint-name] // Example: .u-block@sm